Primary systemic therapy is allowed if the patient has a clinical T1-2N0 status (initial stage) that is amenable to lumpectomy pre-systemic therapy.

- Exclusion criteria

1. Clinically node positive pre-operative
2. Bilateral breast cancer
3. Evidence of metastatic disease
4. History of invasive breast cancer
5. Previous treatment of the ipsilateral axilla with surgery or radiotherapy, except surgery for hidradenitis suppurativa or for other superficially located skin lesions, such as naevi
6. Pregnant or nursing
7. Other prior malignancies within the past 5 years, except successfully treated malignancies that occurred more than five years before randomization, and except successfully treated basal cell and squamous cell skin cancer, carcinoma in situ of the cervix or carcinoma in situ of the ipsilateral or contralateral breast

- mec approval received

yes

- multicenter trial

yes

- randomised

yes

- masking/blinding

Single

- control

Active

- group

Parallel

- Type

2 or more arms, randomized

- Studytype

intervention

- planned startdate

18-mei-2015

- planned closingdate

18-mei-2027

- Target number of participants

1644

- Interventions

Arm A (control arm): lumpectomy with sentinel lymph node procedure, followed by radiotherapy of the breast with or without completion axillary treatment according to the Dutch guideline.

Arm B (study arm): lumpectomy without further axillary staging, followed by radiotherapy of the breast.